Handheld two-way radio transceivers (also known as cell phones) are well known in the art. Recent designs for such transceivers do not require a manually extendable antenna for cellular operation. It is also known to provide cellular phones with the feature of receiving a GPS signal from a GPS satellite for determining location of the cell phone. GPS refers generically to satellite positioning systems comprising a system or constellation of navigation satellites orbiting a celestial body. Exemplary earth-orbiting satellite positioning system constellations include NAVSTAR GPS, GLONASS, and Galileo. Cell phones receive GPS signals so that operators in a public safety answering center are able to determine the location of the cell phone by receiving a GPS signal via the cell phone. This feature assists in locating cell phones and their users during emergency situations. In the Global Positioning System each GPS satellite transmits its own position, its time, and a long pseudo random noise code. The noise code is used by the receiver to calculate range. Satellite position and time are derived from on-board celestial navigation equipment and atomic clocks accurate to one second in 300,000 years. But the ranging is the heart of GPS. Both in the receiver, and in the satellite, a very long sequence of apparently random bits are generated. By comparing internal stream of bits in the receiver to the precisely duplicate received bits from the satellite, and “aligning” the two streams, a shift error or displacement can be calculated representing the precise travel time from satellite to receiver. Since the receiver also knows the precise position of the satellite, and its range from the receiver, a simple triangulation calculation can give two dimensional position (lat/long) from three satellites and additional elevation information from a fourth.
In many situations a blocked environment such as inside a building or a parking garage, GPS does not work well because of the limited visibility the GPS antenna has to the positioning satellites. In such cases, the transceiver may receive inadequate signal power to effectively determine a position of the transceiver. A further factor for inadequate signal power is that the presence of the user in close proximity to the GPS antenna reduces the signal power. Field testing with server assisted GPS technology has shown that the sensitivity of transceivers is approximately −150 dBm. Testing has also shown that the signal strength of the satellites is approximately −155 dBm to −160 dBm in blocked environments. This means that an increase in sensitivity of between 5 dB and 10 dB is required for improved performance. In the prior art this level of improvement is achieved using larger antennas that are held away from the body of the user and that are manually deployed. However, the design of modern day cell phones does not provide the option of an antenna which can be manually deployed by the user.
Thus, there is a need in the prior art for an automatically deployable antenna for receiving GPS signals, especially in emergency situations.